Post on 21-Jan-2016
ALNA- Accelerator Laboratory for NuclearAstrophysics Underground
Heide Costantini
University of Notre Dame, IN, USAINFN, Genova, Italy
Outline:Outline:
• LUNA:LUNA:- - an example of experimental nuclear astrophysics an example of experimental nuclear astrophysics
laboratory UNDERGROUND laboratory UNDERGROUND
• ALNA: ALNA: - goalgoal- methodsmethods- experimental techniquesexperimental techniques
• Nuclear astrophysics:Nuclear astrophysics: - main reactions - main reactions - experimental problems- experimental problems
the abundance of the elements in the Universe
0 10 20 30 40 50 60 70 80 90
10-2
102
104
106
108
1010
1
Atomic number
rela
tive
ab
un
dan
ce
the ambitious task ofNuclear Astrophysics
is to explain the originand relative abundance
of the elements in the Universe
elements are produced inside stars during their life
n-capture, -decay,…N-ToF, RIA
Charged particlesFusion reactions
Fe
p + p d + e+ + ep + p d + e+ + e
d + p 3He + d + p 3He +
3He +3He + 2p3He +3He + 2p 3He +4He 7Be +
3He +4He 7Be +
7Be+e- 7Li + +e7Be+e- 7Li + +e 7Be + p 8B +
7Be + p 8B +
7Li + p + 7Li + p + 8B 2+ e++ e
8B 2+ e++ e
84.7 % 13.8 %
13.78 % 0.02 %
pp chain
12C 13Np,
-
13C
14N
p,
15O
+
15N
p,
p,
CNO cycle
produces energy for most of the life of the stars
4p 4He + 2e+ + 2e + 26.73 MeV
Hydrogen burning
Two questions remain relevant: Energy production and timescale:
4He(2,)12C(,)16O(,)20Ne
Neutron production for weak s-process:
14N(,)18F(+)18O(,)22Ne(,n) 22Ne(,)
Neutron production for fast s-process:
13C(,n)
1212C(C(,,))1616OO
Triple Triple
4He
16O12C
4He
20Ne
1616O(O(,,))2020NeNe
4He
Helium burning
The extrapolation problem
?
extrapolation is needed….
??S(E
)
fact
or
S(E) = E·(E)·exp(2)
(E) = S(E)·exp(-2) /E
2 = 31.29 Z1 Z2 (/E)0.5
sometimes extrapolation fails !!
RRlablab >> B Bcosmcosm+ + BBenvenv ++ BBbeambeam inducedinduced
Environmental radioactivity has to be considered underground (shielding) and intrinsic detector bck
Beam induced bck from impurities in beam & targets high purity and detector techniques (coincidence)
Cross section measurement requirements
1,00E-06
1,00E-05
1,00E-04
1,00E-03
1,00E-02
1,00E-01
1,00E+00
0 2000 4000 6000 8000 10000
E[keV]
coun
ts
1,00E-06
1,00E-05
1,00E-04
1,00E-03
1,00E-02
1,00E-01
1,00E+00
0 2000 4000 6000 8000 10000
E[keV]
coun
ts
3MeV < E3MeV < E< 8MeV: < 8MeV: 0.5 0.5 Counts/sCounts/s
3MeV < E3MeV < E< 8MeV < 8MeV 0.0002 Counts/s
GOINGUNDERGROUND
HpGeHpGe
LUNA site
LUNA 1(1992-2001)
50 kV
LUNA 2(2000…)
400 kV
LLaboratory foraboratory for UUndergroundnderground
NNuclear uclear AAstrophysicsstrophysics
Radiation
LNGS/surface
MuonsNeutron
sPhotons
10-6
10-3
10-1
LNGS(shielding 4000 m w.e.)
Measurements @ LUNA
12C 13Np,
-
13C
14N
p,
15O
+
15N
p,
p,
CNO cycle
p + p d + e+ + ep + p d + e+ + e
d + p 3He + d + p 3He +
3He +3He + 2p3He +3He + 2p 3He +4He 7Be +
3He +4He 7Be +
7Be+e- 7Li + +e7Be+e- 7Li + +e 7Be + p 8B +
7Be + p 8B +
7Li + p + 7Li + p + 8B 2+ e++ e
8B 2+ e++ e
84.7 % 13.8 %
13.78 % 0.02 %
pp chain
3He(4He,)7Be14N(p,)15Od(p,)3He
3He(3He,2p)4He
Energy spread 70eV
Long term stability: 5 eV/h
U = 50 – 400 kVI 500 A for protonsI 250 A for alphas
LUNA II
Q = 7.3 MeV
- 504
-21
278
1414N+pN+p72977297
7556
7276
6859
6793
6176
5241
5183
0
1/2 +
7/2 +
5/2 +
3/2 +
3/2 -
5/2 +
1/2 +
1/2 -
1515OO
1414N(p,N(p,))1515OO
gas target
beam
Reaction Rate = 10.95 0.83 c/dBackground rate = 21.14 0.75 c/d
t = 49.12 days
Q = 9277 C
Spectrum 70 keVSpectrum 70 keV
BGO summingcrystal
LUNA main results
High beam current
Event identification
High efficiency detector
Pure gas target
full advantage Underground lab
• Lowest energy: 2cts/month
• Lowest cross section: 0.02
pbarn
• Background < 4*10-2 cts/d in
ROI
3He(3He,2p)4He1414N(p,N(p,))1515
OO
Low cosmic background
Goal at ALNA:• systematic study of reactions relevant for the understanding of He-burningHe-burning and C-C-burningburning in red giants, AGB stars and late evolutionary stages
Accelerators:
installation of a small (2 MV terminal Voltage) accelerator to study (,n) and (,) reactions in forward kinematics
•1st phase:
heavy ion accelerator for inverse kinematics studies (M. Couder’s talk)(M. Couder’s talk)
•2nd phase:
• energy calibration: < 0.1%
• Energy resolution: < 0.1%
• long-term stability: > days to months
• beam intensity: I > 100 A
• Energy range: 100kV-2MV
• Beam: p,
• Count rate limitation of 1 ev/day > 0.2 nbarn
Accelerator Requirements1st phase
• high efficiency increase counting rate
• Low intrinsic activity
• Passive shielding
• event identification
• active shielding decrease beam-induced background
decrease environmental background
Detector facility requirements1st phase
Example: 19F(p,-)16O background reduction by Q-value gating for 19F(p,)20Ne
counts
E
counts
E
Facility requirements
• Depth shielding 4000 (mwe)
• Space 15X10X5 (m3) accelerator 15x10x5 (m3) (target
room 1st phase) 15X20X5 (m3) (target room 2nd phase)
• Electrical power 50 kW (1st phase)200 kW (2nd phase)
•Additional facilities machine shoppower supply
low level countingDI water systemcompressed airLN25 ton crane in target area
Contributors and collaborators:
A. Champagne University of North Carolina
R. Clark LBNL
M. Couder University of Notre Dame
M. Cromaz LBNL
A. Garcia University of Washington
J. Görres University of Notre Dame
U. Greife Colorado School of Mines
C. Iliadis University of North Carolina
D. Leitner LBNL
P. Parker Yale University
K. Snover University of Washington
P. Vetter LBNL
M Wiescher University of Notre Dame